In a communication system, RSs are mainly used to assist a receiving end in obtaining a channel estimation value hi,j (hi,j indicates a channel estimation value between a jth transmitting antenna and an ith receiving antenna) of each antenna port. Furthermore, RSs are also used for the receiving end to perform various measurements, such as, the Channel Quality Indicator (CQI) measurement and the Precoding Matrix Indicator (PMI) measurement. To facilitate the receiving end to perform channel estimation, when an antenna j (1<=j<=M, and M is a supported maximal number of transmitting antenna ports) sends RSs, no other antennas k (k≠j) in the corresponding time-frequency resource send any signals.
Taking a Long Term Evolution (LTE) communication system of 3GPP as an example, the downlink transmission of the LTE communication system supports at most four antenna ports, and an average overhead occupied by the specific RSs of the corresponding cell is up to 14.3%. With the evolution of the communication system, the evolved system (referred to as an enhanced system, and the system before evolution is referred to as an original system) will be required to support more antenna ports, and a transmission device in the evolved system is required to be compatible with a receiving device in the original system.
For example, in an LTE Advanced system (enhanced system), the number of downlink transmitting antennas may be expanded to eight, so how to design RSs under the enhanced system so that the enhanced system can obtain gains from the added antennas and at the same time the enhanced system is compatible with the original system becomes an important problem to be solved necessarily.
Presently, there is a solution of simple expansion based on the original system, that is, eight antennas of the enhanced system send RSs on different time-frequency resources respectively. During the implementation of the present invention, the inventor found that the prior art at least has the following problems.
On one hand, an RS sequence of newly added four antenna ports needs to be designed, so large modification is made on the original system; and on the other hand, the system overhead of the RSs is increased.